The cellular communications industry has experienced very rapid growth in both the areas serviced and the number of subscribers. It is not uncommon in many metropolitan areas for mobile switching centers (MSCs) to have service requests numbering in excess of 100,000 call attempts per hour. In these metropolitan areas, each MSC may serve a network of 100 or more cell sites, or base stations, each of which defining a particular cell. Each MSC also keeps track of all mobile units, such as cellular telephones, currently operating in its service area via a database commonly referred to as a visitor location register (VLR). This register stores information regarding the services available to each subscriber, his home MSC and the current status (e.g., active or inactive) of the mobile unit. The MSC, however, does not usually have accurate information regarding the precise geographical location of each of the mobile units within the service area.
When a call is initiated to a mobile unit believed to be within the service area, a page must be broadcast over a forward control channel to all cells in the service area. The mobile unit responds to the page by providing a unique number that identifies the mobile unit. When the mobile unit responds to the page, the particular cell containing the mobile unit is then identified from a reverse control channel used for the mobile response and a cellular link is then set up. When a call is initiated from a mobile unit it simply broadcasts the unique number that identifies the unit. If a cell (as well as the servicing MSC) recognizes the unique number, as well as other certain parameters, a cellular link is established with the mobile unit.
As cellular phone usage has increased, cellular fraud has become more and more prevalent. Cellular fraud occurs when an unauthorized cellular device uses the unique number associated with a legitimate mobile unit. Once the unique number has been discovered, the unauthorized cellular device may utilize the cellular communication network at the expense of the legitimate mobile unit. Furthermore, due to the very nature of mobile units, it is extremely difficult to track down the unauthorized device.
Certain proposals have been discussed for combining a positioning system, such as a system that relies on signals from a global positioning satellite, with a mobile unit. One such proposal is described in a U.S. patent application Ser. No. 08/792,771 entitled "Method and Apparatus for Using Advanced Positioning Systems in Cellular Communication Networks", which is hereby incorporated by reference thereto. Such proposals have not addressed fraudulent use of a mobile unit's unique number, as described above.
Therefore, what is needed is a system that helps to prevent fraudulent use of a cellular communications network.
Furthermore, what is needed is a system that assists in providing location information for a mobile unit operating in the cellular communications network.